Comcast Corp. has grown into one of the biggest corporate-lobbying presences in Washington. Recently its influence has been put to the test, as reported in a page-one article in The Wall Street Journal.

Comcast Corp. and Time Warner Cable Inc. fired back at critics of their $45 billion proposed merger, defending the transaction against concerns it would make Comcast the gatekeeper of the online and pay TV world.

As the FCC reviews Comcast's proposed purchase of Time Warner Cable, the agency is encouraging media companies to offer feedback confidentially. One gripe: a practice that gives cable giants the same terms as competitors.

A Comcast executive said the company's planned $45 billion acquisition of Time Warner Cable would create new competition in the commercial market for broadband Internet access without harming home users or content companies.

Comcast Corp. agreed to buy Time Warner Cable for about $45.2 billion in stock, in a deal that would combine the nation's two biggest cable operators. Here's a recap of the conference call analyzing the details of the deal.

Comcast's lengthy filing to regulators, to justify its $45 billion proposed purchase of Time Warner Cable, shows the many ways the combined entity could use its leverage over both cable lines and programming to pressure competitors.